Obama announced his support for gay marriage a day after North Carolina, which he won narrowly in 2008, voted for a constitutional ban on such unions. The Democratic convention is in Charlotte, but that's no guarantee.

Washington — As of Wednesday, President Obama now openly supports gay marriage. North Carolina voters, just a day earlier, decided by a wide margin to amend their constitution to ban gay marriage and civil unions.

And in the first week of September, Mr. Obama and the Democrats will gather in the state’s largest city – Charlotte – for their quadrennial convention.

Even though Obama won the Tar Heel State by only three-tenths of a percent in 2008, his team hoped he could build on that success and win again there in 2012, especially with all the attention and money lavished by the convention.

But that decision was set two years ago, and so Charlotte it will be. Maybe North Carolina's electoral votes were already a lost cause before the president announced his support for gay marriage, given the sour mood of voters over the economy. But if he is to have any chance at all of winning the state again – he was the first Democrat to do so since Jimmy Carter in 1976 – he will have to watch two key groups: swing voters and African Americans.

Swing voters, typically based in suburbs, matter everywhere. They are, by definition, the deciders in battleground states. But the African American question could be trickier. While national polls show that a majority of white voters support gay marriage, among African Americans, support lags. Last year, a Washington Post/ABC News poll put the percentage of black support for gay marriage at 42 percent, with 55 percent opposing.

African Americans are a crucial part of Obama’s base, and he needs them to turn out for him. Given his status as the first black president, Obama has commanded fierce loyalty among black voters.

But consider the gay marriage vote in North Carolina: Some majority black counties that went big for Obama four years ago were just as strong in their support for the anti-gay-marriage amendment on Tuesday.

“For example, Hertford County, with a 60 percent black population, voted for Obama with 70 percent in 2008 and on Tuesday 70 percent of its voters backed the constitutional amendment defining marriage,” MSNBC reports.

“And Halifax County, with a 53 percent black population, voted for Obama with 64 percent in 2008 and backed the amendment with 68 percent of its votes.”

An expert on the black vote says Obama need not worry.

“The turnout and the result [on Tuesday] mean nothing for November,” says Kerry Haynie, co-director of the Center for the Study of Race, Ethnicity and Gender in the Social Sciences at Duke University in Durham, N.C.

Historically, he says, black voters have been conservative on social issues, such as abortion, gay marriage, and prayer in schools. But that rarely if ever has turned into votes for Republicans. And he doubts they will stay home.

“Many of those African Americans who voted for the amendment will come back and vote for Obama and other Democratic candidates,” says Professor Haynie. “African Americans tend to vote on economic issues, and the Democrats continue to have an advantage there.”

Overall, the anti-gay-marriage measure in North Carolina won handily, with 61 percent voting yes on Amendment One. Same-sex marriage was already against the law in North Carolina, and by amending the state constitution, it will be harder to change course in the future. Opponents of the measure say that many voters didn’t understand that its impact goes beyond banning gay marriage. The amendment states that “marriage between one man and one woman is the only domestic legal union that shall be valid or recognized in this state.” That leaves civil unions and potentially other domestic partnerships without legal recognition.

Obama opposed the ballot measure, and his campaign reported he was disappointed by the outcome.

“The president has long opposed divisive and discriminatory efforts to deny rights and benefits to same-sex couples," Obama's North Carolina spokesman, Cameron French, said in a statement released before the president announced his support for gay marriage.

"He believes the North Carolina measure singles out and discriminates against committed gay and lesbian couples, which is why he did not support it. President Obama has long believed that gay and lesbian couples deserve the same rights and legal protections as straight couples and is disappointed in the passage of this amendment," Mr. French said.

As for any political benefits or risks involved in having the 2012 Democratic convention in North Carolina, chances are it won’t make a difference to Obama’s reelection prospects. Academics have found no evidence that the choice of convention location has an impact either way on whether a candidate wins that state.

And furthermore, analysts don't see winning North Carolina is crucial to Obama's reelection.